1. Field of the Invention
The present invention relates to a material for organic electroluminescence device and the organic electroluminescence device.
2. Description of the Related Art
Research and development are being vigorously made on organic electroluminescence devices (which may hereinafter be referred to as “devices” or “organic EL devices”) because they can emit light with high brightness even by low voltage driving. In general, organic electroluminescence devices each has one or more organic layers including a light emitting layer and a pair of electrodes sandwiching them therebetween. For light emission, they utilize energy of an exciton generated as a result of recombination, in the light emitting layer, of electrons injected from a cathode and holes injected from an anode.
In recent years, phosphorescent materials have been used for the purpose of increasing the efficiency of devices. For example, use of an iridium or platinum complex as a phosphorescent material has been studied in order to provide an organic electroluminescence device having improved emission efficiency and heat resistance.
In addition, doped devices using a light emitting layer obtained by doping a light emitting material in a host material have been employed widely.
Patent Document 1 describes an iridium complex that contains a condensed azole ligand, has high durability, and is blue-light emissive.
Patent Document 2 describes a device using a phosphorescent complex, particularly, an iridium complex containing a structural isomer thereof.
Patent Document 3 describes a method of producing an iridium complex while increasing the purity of a facial isomer thereof.
[Patent Document 1] U.S. Patent Application Publication No. 2008/0297033
[Patent Document 2] JP-A-2006-237306 (The term “JP-A” as used herein refers to an “unexamined published Japanese patent application”.)
[Patent Document 3] JP-A-2007-91718